Enlarged under-jaw glands, or lymph nodes, are usually the result of bacteria or viruses, according to Mayo Clinic. In rare cases, swollen lymph nodes are caused by certain cancers. Doctors diagnose the cause of swollen glands by examining the accompanying symptoms.
Bacterial infections such as strep throat and abscesses can cause swollen glands, especially around the jaw, WebMD explains. Viruses such as measles, rubella, chickenpox or mumps also cause swollen lymph nodes. People who have developed AIDS after an HIV infection commonly have swollen lymph nodes, as the virus attacks the immune system. Mononucleosis causes swollen glands, fever, sore throat and fatigue.
Less common infections that cause swollen glands are Lyme disease and syphilis, reports WebMD. Lyme disease is spread by tick bites, while syphilis is a sexually transmitted infection. Benign growths such as cysts, tonsillitis and inflammation of the fatty tissue under the skin cause swollen glands as well.
The lymphatic system is primarily located in the head and neck region, Mayo Clinic says. When a node becomes swollen, it is a sign that something is wrong somewhere in the body. Symptoms include tender and painful nodes, glands that swell to the size of a kidney bean or swollen limbs. Swelling in the nodes stops after the body has been cleared of infections. Swollen glands that have been present for more than two weeks, that are accompanied by high fever, or that cause difficulty swallowing and breathing require immediate medical attention.